In English language, the one letter words are: I and A. So if you see a symbol in the code that is just one symbol forming word - chances are it is I or A.

As mj2c mentioned - in words that are made up of several symbols; the more often the symbols are found might be deduced that they are vowels (a, e, i, o or u). Then you deduce if that is so or try them and see if a word is formed.

Then if a 2 similar symbols are side by side; they might be those letters that are commonly seen in English words: tt, ll, oo...

I was just going to "see what happens", and I ended up completing 55% of the game (according to the counter). This is the farthest I have ever gotten in an adventure game without a walkthrough; I'm quite proud of myself.

I'm stuck now at Montfaucon, though. I have no idea how to get rid of the cop outside. Do you have any tips?

(I don't want to check a walkthrough; I might risk spoiling the game for myself)

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Are they dead? Yes. Unlike you they have but one life...and they wasted it for your sake!

In Montfaucon, the policeman should be sat at a table outside a cafe. A manhole cover should be set in the ground away to his right, with a juggler standing close by to it, juggling. Is this where you're at? Maybe describe your surroundings so we can tell. I haven't played the Director's Cut, so I'm not sure if there are differences?